This invention relates to air or pneumatic powered guns, and, more particularly, to a pressure relief valve for an air gun which limits the velocity of projectiles fired by the guns regardless of the number of pumps.
A pneumatic or air powered gun conventionally includes a pressure reservoir for storing pressurized air and firing means for releasing the pressurized air to propel a projectile out of the barrel. Pressure is usually built up in the reservoir by a hand pump mounted on the gun, and the pressure in the reservoir is increased each time the pump is operated. However, variations in the amount of pumping affect the performance of the gun. Excessive muzzle velocity caused by over-pumping may violate government regulations in some jurisdictions. Excessive pressure also causes abnormal wear and damages to components of the gun. Over-pumping can also result in all of the pressure not being released when the gun is fired, and an unexpected discharge might occur without the gun being pumped if the trigger is again pulled. Under-pumping creates a weak muzzle velocity and inaccurate shots.
Pressure relief valves have been employed to control the maximum pressure in guns and other devices. For example, U.S. Pat. Nos. 1,486,215, 3,025,633, 3,680,540, and 4,304,213 disclose valves for shunting air away from the projectile to reduce muzzle velocity when the pressure reaches a certain limit. However, none of the foregoing patents describes a pressure relief valve which is mounted directly within the pump piston.